The present invention relates to apparatus and processes used for abatement of by-products generated when cleaning depositions left in a chamber used to deposit layers of material in semiconductor manufacturing processes.
During a typical CVD (i.e., chemical vapor deposition) process, deposition gas or gases inside a processing chamber form a thin film layer on the surface of a substrate being processed. Some CVD processes react two or more gases together to form the desired layer. For example, an oxygen source gas may be mixed with a silane source gas to form a type of silicon dioxide layer. Organosilanes also may be used as precursor gases, and are oxidized to form organosilicon oxides. During the deposition of a layer, not only does the substrate become covered with the material forming the layer, but other exposed surfaces within the chamber receive deposits as well. With repetition of the deposition process, the CVD chamber eventually will need to be cleaned because of the accumulation of deposits from each deposition process. Left uncleaned, at some point these deposits can crack and fall or flake off, with a possibility of contaminating the substrate that happens to be in the chamber for processing at the time.
As a result, CVD chambers must be periodically cleaned to remove deposits which accumulated within the chamber with each deposition process. A typical method of cleaning involves the introduction of cleaning gases into the chamber to react with the deposited material to form a product or products that can be exhausted from the chamber. U.S. Pat. No. 6,060,397 discloses examples of such cleaning processes, for example. Typically, a cleaning gas such as a fluorinated gas is introduced into the chamber and a plasma (using RF, or microwave energy, for example) is struck in the chamber. The resultant excited products react with the deposition materials to form gaseous by-products which are then exhausted from the chamber.
Unfortunately, many of these by-products are hazardous air pollutants, which pose a strong environmental concern as they may negatively effect such problems as global warming, ozone deterioration, etc. Consequently, various abatement procedures have been developed in an effort to minimize or eliminate the hazardous air pollutants before they can be released to the atmosphere.
The most common tool designs use an incinerator, such as a Guardian 4 (available from Boc Edwards, Santa Clara, Calif.), which treats flammable and oxidizing gases and allows corrosive gases to pass through to be treated by a scrubbed exhaust system. Although this system is widely used and has a relatively small footprint, it is susceptible to heavy use of corrosive gases which may significantly shorten its life span, and more than one unit may be needed to adequately abate cleaning by-products from a chamber capable of processing 300 mm wafers. More importantly, this system does not remove hazardous air pollutants, such as F2 from the exhaust gases.
Another tool, known as an adsorption or dry scrubber uses resin bottles in cabinets that collect the exhausted by-products and chemically convert the gases to solid by-products which then remain in the bottles. However, hydrogen is not treated by this tool and therefore an incinerator is still needed for treating hydrogen. The life span of the bottles is also short, sometimes as short as twenty days. Disposal fees for the spent bottles are also high. Some applications require two of these scrubbers, one for NF3 and one for flammable gases.
Another tool, known as a CDO (Controlled Decomposition/Oxidation Unit), such as the Delatech 857, Delatech 858 or Delatech 880, for example, uses a two stage process in which the exhaust is first oxidized at high temperatures and then scrubbed with water to remove particulates and mineral acids. This type of system requires a wastewater stream of about two gallons per minute, the drainage of which can be problematic, and the system itself is also very expensive and requires an additional space on the processing floor, due to its footprint.
Thus, there remains a need for a clean, efficient and relatively inexpensive abatement system for abatement of by-products generated when cleaning depositions left in a chamber used to deposit layers of material in semiconductor manufacturing processes. Since F2 cannot be effectively incinerated or scrubbed, there is a particular need for an abatement apparatus that efficiently and cost effectively abates F2. A reduction in footprint of such a device, as compared to abatement tools currently in use would also be welcomed.